Various types of combustors are known and used in gas turbine engines. In turn, these combustors generally use different types of fuel burners or nozzles depending upon the type of fuel in use. For example, most natural gas fired systems operate using lean premixed flames. In these systems, fuel is mixed with air upstream of the reaction zone to create a premixed flame. One example is a “swozzle” (swirler+nozzle) in which the fuel ports are positioned about a number of extending vanes so as to inject the fuel into the air stream. Alternatively in systems using syngas or other types of fuels, diffusion nozzles may be used to inject the fuel and the air directly into the combustion chamber due to the generally higher reactivity of the fuel.
Current combustor designs, however, focus on fuel flexibility with respect to the use of natural gas and other types of fuels. As a result, operational issues may arise when switching from one type of fuel to another while using the same components. For example, syngas may have a much higher volumetric flow rate as opposed to natural gas due to its lower Modified Wobbe Index. As a result of this and the high reactivity of some of these fuels, flame holding issues may arise. The design of the combustor and its components thus should accommodate these varying fuel characteristics such as different fuel reactivities, fuel temperatures, heating values, molecular weight, etc.
There is thus a desire for improved combustor components in general and an improved burner in specific. Such a burner may provide for good fuel and air mixing for greater fuel flexibility while maintaining system efficiency and limiting overall emissions. Such fuel flexible systems should accommodate natural gas and other types of fuels without expensive equipment changeovers.